The pictures show fiber washers under the heads of the screws securing the sending unit.  The plans do not.  Should they ?

 

Also, what are folks using for sealing the threads ?

 

Last question ... the sending unit comes with a rubber gasket and the mounting kit comes with another.  It looks like only one (on TOP of the

tanks skin) is required.

 

Thanks for your help.

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I called the Factory about those same concerns.  The sender only takes one gasket.  The kit supplied one and the gauge mfg. supplied another.  ZAC told me the fiber washers are not longer used.  I spread a small amount of thread lubricant/ sealer purchased from an automotive store on the screw threads.  Make sure it is fuel resistant.  I relied on the advice from the clerk.  I tested each tank for leaks for two hours, no leaks showed up.

Don Herbel

Claremore OK

Don;   Thanks for the info.   It's hard for me to picture how gas can't get between the "backing plate" and the underside of the tank skin, and then wick up the screw.  I wonder why they don't use a gasket on the underside as well.

Gordon,

I bought the "expensive" fuel resistant sealant from Aircraft Spruce because I didn't want to think about a problem.  Testing is a good idea too.

Be sure to put sealant on the screw threads as well otherwise it could wick up.

Best,

Joe

ps

If you're building a 750 you've got an access panel on the bottom wing skins. If its a 701 (like mine)  seriously consider them so you can address fuel line /  sender issues without having to deskin.

Gordon, I agree with Don in that you only need to use one of the gaskets on the outside of the tank. To seal the heads of the screws and the gasket, I applied a a thin layer of fuel lube under the gasket and a much more generous layer on the heads of the screws and around the edges of the gasket. Fuel lube is available at:

http://www.aircraftspruce.com/catalog/cspages/ezturnlube.php

My senders are on the ends of the tanks and I have not had any leaks in this area after several tanks of 100LL.  

Regards,

Dave

Thanks for all the responses.   I'm building a 750 so I've already got an access panel.  I'll just use the one rubber gasket, on the outside of the skin, and make sure to seal the threads and the heads of the screws with an

appropriate sealant.

Hi, i just want to warn about a issue: (if you do everything perfect with the installation of the sender-unit and use the gaskets under the screws)

You do not have a grounding.......(the instrument need ground to work)

If you  mount it totaly in the center of the gastank hole (no metal contackt), and all the screw are in the middle of the holes (no metal contact)

I ended up welding a groundpoint on the sender-unit. Because i used the gasket under each screw, this becomes a issue!

(and i used Locktite thread-sealer on the threads to)

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